Integrated Ultrasound-Assisted Convective–Microwave Drying for the Dehydration of Medicinal Plants

Abstract Ultrasound-assisted convective-microwave drying (UACMD) is an emerging hybrid drying method that combines hot-air convection, microwave heating and ultrasound cavitation to enhance moisture transfer and preserve bioactive compounds in medicinal herbs. This review summarizes its advantages, including a 30-80% reduction in drying time, improved energy efficiency, and better retention of antioxidants, essential oils, and color. However, challenges, such as thermal degradation and scale-up complexity remain. Future developments emphasize the integration of smart controls (artificial intelligence, computer vision, and hyperspectral imaging) and the tailoring of protocols for specific herb types, positioning UACMD as a sustainable and high-performance solution for modern herbal drying.